Use the echelon method to solve the system of three equations in three unknowns.

1. x-y+2z=-2
5x + z=0
x+2y+z=4

2. Determine the equation of the line described. Put the answer in the slope -intercept form, if possible. Through (-7,-7), parallel to 5x-4y=-19

Write a word or phrase that best completes each statement or answers the question.

3. If a company decides to make a new product, there are fixed costs and variable costs associated with this new product. Explain the differences of the two types of costs and why they occur. Use an example to illustrate your point.